Offloading of computation for rack level servers and corresponding methods and systems

ABSTRACT

A distributed server system for handling multiple networked applications is disclosed. Systems can include at least one main processor; a plurality of offload processors connected to a memory bus; an arbiter connected to each of the plurality of offload processors, the arbiter configured to schedule resource priority for instructions or data received from the memory bus; and a virtual switch respectively connected to the main processor and the plurality of offload processors using the memory bus, with the virtual switch capable of receiving memory read/write data over the memory bus, and further directing at least some memory read/write data to the arbiter.

PRIORITY CLAIMS

This application claims the benefit of U.S. Provisional PatentApplications 61/650,373 filed May 22, 2012, 61/753,892 filed on Jan. 17,2013, 61/753,895 filed on Jan. 17, 2013, 61/753,899 filed on Jan. 17,2013, 61/753,901 filed on Jan. 17, 2013, 61/753,903 filed on Jan. 17,2013, 61/753,904 filed on Jan. 17, 2013, 61/753,906 filed on Jan. 17,2013, 61/753,907 filed on Jan. 17, 2013, and 61/753,910 filed on Jan.17, 2013, the contents all of which are incorporated by referenceherein.

TECHNICAL FIELD

The present disclosure relates generally to servers, and moreparticularly to offload or auxiliary processing modules that can bephysically connected to a system memory bus to process data independentof a host processor of the server.

BACKGROUND

Networked applications often run on dedicated servers that support anassociated “state” for context or session-defined application. Serverscan run multiple applications, each associated with a specific staterunning on the server. Common server applications include an Apache webserver, a MySQL database application, PHP hypertext preprocessing, videoor audio processing with Kaltura supported software, packet filters,application cache, management and application switches, accounting,analytics, and logging.

Unfortunately, servers can be limited by computational and memorystorage costs associated with switching between applications. Whenmultiple applications are constantly required to be available, theoverhead associated with storing the session state of each applicationcan result in poor performance due to constant switching betweenapplications. Dividing applications between multiple processor cores canhelp alleviate the application switching problem, but does not eliminateit, since even advanced processors often only have eight to sixteencores, while hundreds of application or session states may be required.

SUMMARY

A distributed server system can include at least one main processor; aplurality of offload processors connected to a memory bus; an arbiterconnected to each of the plurality of offload processors, the arbiterconfigured to schedule resource priority for instructions or datareceived from the memory bus; and a virtual switch respectivelyconnected to the main processor and the plurality of offload processorsusing the memory bus, with the virtual switch capable of receivingmemory read/write data over the memory bus, and further directing atleast some memory read/write data to the arbiter

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows illustrates an embodiment with a group of web servers thatare partitioned across a group of brawny processor core(s) and a set ofwimpy cores housed in a rack server.

FIG. 2 shows an embodiment with an assembly that is favorably suited forhandling real time traffic such as video streaming.

FIG. 3 shows illustrates an embodiment with a proxy server-web serverassembly that is partitioned across a group of brawny processor core(s)(housed in a traditional server module) and a set of wimpy cores housedin a rack server module.

FIG. 4-1 shows a cartoon schematically illustrating a data processingsystem according to an embodiment, including a removable computationmodule for offload of data processing.

FIG. 4-2 shows an example layout of an in-line module (referred to as a“XIMM”) module according to an embodiment.

FIG. 4-3 shows two possible architectures for a data processing systemincluding x86 main processors and XIMMs (Xockets MAX and MIN).

FIG. 4-4 shows a representative the power budget for XIMMs according tovarious embodiments.

FIG. 4-5 illustrates data flow operation of one embodiment of a XIMMusing an ARM A9 architecture.

FIG. 5-1 is a block schematic diagram of a processing module accordingto an embodiment.

FIGS. 5-2 and 5-3 are diagrams of a processor module according toembodiments.

FIG. 5-4 is a diagram showing an opposing side of a processor modulelike that of FIG. 5-2 or 5-3, according to an embodiment.

FIG. 5-5 is a diagram of a system according to an embodiment.

FIGS. 5-6 to 5-11 are block schematic diagrams showing processor moduleoperations according to particular embodiments.

FIG. 5-12 is a flow diagram of a method according to an embodiment.

FIG. 5-13 is a flow diagram of a method according to another embodiment.

FIG. 6-1 is a block schematic diagram of a system according to anotherembodiment.

FIG. 6-2 is a diagram showing a system flow according to an embodiment.

DETAILED DESCRIPTION

Networked applications are available that run on servers and haveassociated with them a state (session-defined applications). The sessionnature of such applications allows them to have an associated state anda context when the session is running on the server. Further, if suchsession-limited applications are computationally lightweight, they canbe run in part or fully on the auxiliary or additional processor cores(such as those based on the ARM architecture, as but one particularexample) which are mounted on modules connected to a memory bus, forexample, by insertion into a socket for a Dual In-line Memory Module(DIMM). Such modules can be referred to as a Xocket™ In-line MemoryModule (XIMM), and have multiple cores (e.g., ARM cores) associated witha memory channel. A XIMM can access the network data through anintermediary virtual switch (such as OpenFlow or similar) that canidentify sessions and direct the network data to the correspondingmodule (XIMM) mounted cores, where the session flow for the incomingnetwork data can be handled.

As will be appreciated, through usage of a large prefetch buffer or lowlatency memory, the session context of each of the sessions that are runon the processor cores of a XIMM can be stored external to the cache ofsuch processor cores. By systematically engineering the transfer ofcache context to a memory external to the module processors (e.g., RAMs)and engineering low latency context switch, it is possible to executeseveral high-bandwidth server applications on a XIMM provided theapplications are not computationally intensive. The “wimpy” processorcores of a XIMM can be favorably disposed to handle high networkbandwidth traffic at a lower latency and at a very low power whencompared to traditional high power ‘brawny’ cores.

In effect, one can reduce problems associated with session limitedservers by using the module processor (e.g., an ARM architectureprocessor) of a XIMM to offload part of the functionality of traditionalservers. Module processor cores may be suited to carry computationallysimple or lightweight applications such as packet filtering or packetlogging functions. They may also be suited for providing the function ofan application cache for handling hot-code that is to be serviced veryfrequently to incoming streams. Module processor cores can also besuited for functions such as video streaming/real time streaming, thatoften only require light-weight processing.

As an example of partitioning applications between a XIMM with “wimpy”ARM cores and a conventional “brawny” core (e.g., x86 or Itanium serverprocessor with Intel multicore processor), a computationally lightweightApache web server can be hosted on one or more XIMMs with ARM cores,while computationally heavy MySQL and PHP are hosted on x86 brawnycores. Similarly, lightweight applications such as a packet filter,application cache, management and application switch are hosted onXIMM(s), while x86 cores host control, accounting, analytics andlogging.

FIG. 1 illustrates an embodiment with a group of distributed web serversthat are partitioned across a group of brawny processor core(s) 108connected by bus 106 to switch 104 (which may be an OpenFlow or othervirtual switch) and a set of wimpy XIMM mounted cores (112 a to 112 c),all being housed in a rack server module 140. In some embodiments, arack server module 140 further includes a switch (100), which can be anetwork interface card with single root IO virtualization that providesinput-out memory management unit (IOMMU) functions 102. A second virtualswitch (104) running, for example, an open source software stackincluding OpenFlow can redirect packets to XIMM mounted cores (112 a to112 c).

According to some embodiments, a web server running Apache-MySQL-PHP(AMP) can be used to service clients that send requests to the servermodule 140 from network 120. The embodiment of FIG. 1 can split atraditional server module running AMP across a combination of processorscores, which act as separate processing entities. Each of the wimpyprocessor cores (112 a to 112 c) (which can be low power ARM cores inparticular embodiments) can be mounted on an XIMM, with each core beingallocated a memory channel (110 a, 110 b, 110 c). At least of one of thewimpy processor cores (112 a to 112 c) can be capable of running acomputationally light weight Apache or similar web server code forservicing client requests which are in the form of HTTP or a similarapplication level protocol. The Apache server code can be replicated fora plurality of clients to service a huge number of requests. The wimpycores (112 a to 112 c) can be ideally suited for running such Apachecode and responding to multiple client requests at a low latency. Forstatic data that is available locally, wimpy cores (112 a to 112 c) canlookup such data from their local cache or a low latency memoryassociated with them. In case the queried data is not available locally,the wimpy cores (112 a to 112 c) can request a direct memory access(DMA) (memory-to-memory or disk-to-memory) transfer to acquire suchdata.

The computation and dynamic behavior associated with the web pages canbe rendered by PHP or such other server side scripts running on thebrawny cores 108. The brawny cores might also have code/scriptinglibraries for interacting with MySQL databases stored in hard diskspresent in said server module 140. The wimpy cores (112 a to 112 c), onreceiving queries or user requests from clients, transfer embeddedPHP/MySQL queries to said brawny cores over a connection (e.g., anEthernet-type connection) that is tunneled on a memory bus such as a DDRbus. The PHP interpreter on brawny cores 108 interfaces and queries aMySQL database and processes the queries before transferring the resultsto the wimpy cores (112 a to 112 c) over said connection. The wimpycores (112 a to 112 c) can then service the results obtained to the enduser or client.

Given that the server code lacking server side script is computationallylight weight, and many Web API types are Representational State Transfer(REST) based and require only HTML processing, and on most occasionsrequire no persistent state, wimpy cores (112 a to 112 c) can be highlysuited to execute such light weight functions. When scripts andcomputation is required, the computation is handled favorably by brawnycores 108 before the results are serviced to end users. The ability toservice low computation user queries with a low latency, and the abilityto introduce dynamicity into the web page by supporting server-sidescripting make the combination of wimpy and brawny cores an ideal fitfor traditional web server functions. In the enterprise and privatedatacenter, simple object access protocol (SOAP) is often used, makingthe ability to context switch with sessions performance critical, andthe ability of wimpy cores to save the context in an extended cache canenhance performance significantly.

FIG. 2 illustrates an embodiment with an assembly that is favorablysuited for handling real time traffic such as video streaming. Theassembly comprises of a group of web servers that are partitioned acrossa group of brawny processor core(s) 208 and a set of wimpy cores (212 ato 212 c) housed in a rack server module 240. The embodiment of FIG. 2splits a traditional server module capable of handling real time trafficacross a combination of processors cores, which act as separateprocessing entities. In some embodiments, a rack server module 240further includes a switch (100), which can provide input-out memorymanagement unit (IOMMU) functions 102.

Each of the wimpy processor cores (e.g., ARM cores) (212 a to 212 c) canbe mounted on an in-memory module (not shown) and each of them can beallocated a memory channel (210 a to 210 c). At least one of the wimpyprocessor cores (212 a to 212 c) can be capable of running a tight,computationally light weight web server code for servicing applicationsthat need to be transmitted with a very low latency/jitter. Exampleapplications such as video, audio, or voice over IP (VoIP) streaminginvolve client requests that need to be handled with as little latencyas possible. One particular protocol suitable for the disclosedembodiment is Real-Time Transport Protocol (RTP), an Internet protocolfor transmitting real-time data such as audio and video. RTP itself doesnot guarantee real-time delivery of data, but it does provide mechanismsfor the sending and receiving applications to support streaming data.

Brawny processor core(s) 208 can be connected by bus 206 to switch 204(which may be an OpenFlow or other virtual switch). In one embodiment,such a bus 206 can be a front side bus.

In operation, server module 240 can handle several client requests andservices information in real time. The stateful nature of applicationssuch as RTP/video streaming makes the embodiment amenable to handleseveral queries at a very high throughput. The embodiment can have anengineered low latency context overhead system that enables wimpy cores(212 a to 212 c) to shift from servicing one session to another sessionin real time. Such a context switch system can enable it to meet thequality of service (QoS) and jitter requirements of RTP and videotraffic. This can provide substantial performance improvement if theoverlay control plane and data plane (for handling real timeapplications related traffic) is split across a brawny processor 208 anda number of wimpy cores (212 a to 212 c). The wimpy cores (212 a to 212c) can be favorably suited to handling the data plane and servicing theactual streaming of data in video/audio streaming or RTP applications.The ability of wimpy cores (212 a to 212 c) to switch between multiplesessions with low latency makes them suitable for handling of the dataplane.

For example, wimpy cores (212 a to 212 c) can run code that quicklyconstructs data that is in an RTP format by concatenating data (that isavailable locally or through direct memory access (DMA) from main memoryor a hard disk) with sequence number, synchronization data, timestampetc., and sends it over to clients according to a predeterminedprotocol. The wimpy cores (212 a to 212 c) can be capable of switchingto a new session/new client with a very low latency and performing a RTPdata transport for the new session. The brawny cores 208 can befavorably suited for overlay control plane functionality.

The overlay control plane can often involve computationally expensiveactions such as setting up a session, monitoring session statistics, andproviding information on QoS and feedback to session participants. Theoverlay control plane and the data plane can communicate over aconnection (e.g., an Ethernet-type connection) that is tunneled on amemory bus such as a DDR bus. Typically, overlay control can establishsessions for features such as audio/videoconferencing, interactivegaming, and call forwarding to be deployed over IP networks, includingtraditional telephony features such as personal mobility, time-of-dayrouting and call forwarding based on the geographical location of theperson being called. For example, the overlay control plane can beresponsible for executing RTP control protocol (RTCP, which forms partof the RTP protocol used to carry VoIP communications and monitors QoS);Session Initiation Protocol (SIP, which is an application-layer controlsignaling protocol for Internet Telephony); Session Description Protocol(SDP, which is a protocol that defines a text-based format fordescribing streaming media sessions and multicast transmissions); orother low latency data streaming protocols.

FIG. 3 illustrates an embodiment with a proxy server-web server assemblythat is partitioned across a group of brawny processor core(s) 328(housed in a traditional server module 360) and a set of wimpy cores(312 a to 312 c) housed in a rack server module 340. The embodiment caninclude a proxy server module 340 that can handle content that isfrequently accessed. A switch/load balancer apparatus 320 can direct allincoming queries to the proxy server module 340. The proxy server module340 can look up its local memory for frequently accessed data andresponds to the query with a response if such data is available. Theproxy server module 340 can also store server side code that isfrequently accessed and can act as a processing resource for executingthe hot code. For queries that are not part of the rack hot code, thewimpy cores (312 a to 312 c) can redirect the traffic to brawny cores(308, 328) for processing and response.

In particular embodiments, in some embodiments, a rack server module 240further includes a switch (100), which can provide input-out memorymanagement unit (IOMMU) functions 302 and a switch 304 (which may be anOpenFlow or other virtual switch). Brawny processor core(s) 308 can beconnected to switch 304 by bus 306, which can be a front side bus. Atraditional server module 360 can also include a switch 324 can provideIOMMU functions 326.

The following example(s) provide illustration and discussion ofexemplary hardware and data processing systems suitable forimplementation and operation of the foregoing discussed systems andmethods. In particular hardware and operation of wimpy cores orcomputational elements connected to a memory bus and mounted in DIMM orother conventional memory socket is discussed.

FIG. 4-1 is a cartoon schematically illustrating a data processingsystem 400 including a removable computation module 402 for offload ofdata processing from x86 or similar main/server processors 403 tomodules connected to a memory bus 403. Such modules 402 can be XIMMmodules, as described herein or equivalents, and can have multiplecomputation elements that can be referred to as “offload processors”because they offload various “light touch” processing tasks such HTML,video, packet level services, security, or data analytics. This is ofparticular advantage for applications that require frequent randomaccess or application context switching, since many server processorsincur significant power usage or have data throughput limitations thatcan be greatly reduced by transfer of the computation to lower power andmore memory efficient offload processors.

The computation elements or offload processors can be accessible throughmemory bus 405. In this embodiment, the module can be inserted into aDual Inline Memory Module (DIMM) slot on a commodity computer or serverusing a DIMM connector (407), providing a significant increase ineffective computing power to system 400. The module (e.g., XIMM) maycommunicate with other components in the commodity computer or servervia one of a variety of busses including but not limited to any versionof existing double data rate standards (e.g., DDR, DDR2, DDR3, etc.)

This illustrated embodiment of the module 402 contains five offloadprocessors (400 a, 400 b, 400 c, 400 d, 400 e) however other embodimentscontaining greater or fewer numbers of processors are contemplated. Theoffload processors (400 a to 400 e) can be custom manufactured or one ofa variety of commodity processors including but not limited tofield-programmable grid arrays (FPGA), microprocessors, reducedinstruction set computers (RISC), microcontrollers or ARM processors.The computation elements or offload processors can include combinationsof computational FPGAs such as those based on Altera, Xilinx (e.g.,Artix™ class or Zynq® architecture, e.g., Zynq® 7020), and/orconventional processors such as those based on Intel Atom or ARMarchitecture (e.g., ARM A9). For many applications, ARM processorshaving advanced memory handling features such as a snoop control unit(SCU) are preferred, since this can allow coherent read and write ofmemory. Other preferred advanced memory features can include processorsthat support an accelerator coherency port (ACP) that can allow forcoherent supplementation of the cache through an FPGA fabric orcomputational element.

Each offload processor (400 a to 400 e) on the module 402 may run one ofa variety of operating systems including but not limited to Apache orLinux. In addition, the offload processors (400 a to 400 e) may haveaccess to a plurality of dedicated or shared storage methods. In thisembodiment, each offload processor can connect to one or more storageunits (in this embodiments, pairs of storage units 404 a, 404 b, 404 cand 404 d). Storage units (404 a to 404 d) can be of a variety ofstorage types, including but not limited to random access memory (RAM),dynamic random access memory (DRAM), sequential access memory (SAM),static random access memory (SRAM), synchronous dynamic random accessmemory (SDRAM), reduced latency dynamic random access memory (RLDRAM),flash memory, or other emerging memory standards such as those based onDDR4 or hybrid memory cubes (HMC).

FIG. 4-2 shows an example layout of a module (e.g., XIMM) such as thatdescribed in FIG. 4-1, as well as a connectivity diagram between thecomponents of the module. In this example, five Xilinx™ Zynq® 7020 (416a, 416 b, 416 c, 416 d, 416 e and 416 in the connectivity diagram)programmable systems-on-a-chip (SoC) are used as computationalFPGAs/offload processors. These offload processors can communicate witheach other using memory-mapped input-output (MMIO) (412). The types ofstorage units used in this example are SDRAM (SD, one shown as 408) andRLDRAM (RLD, three shown as 406 a, 406 b, 406 c) and an Inphi™ iMB02memory buffer 418. Down conversion of 3.3 V to 2.5 volt is required toconnect the RLDRAM (406 a to 406 c) with the Zynq® components. Thecomponents are connected to the offload processors and to each other viaa DDR3 (414) memory bus. Advantageously, the indicated layout maximizesmemory resources availability without requiring a violation of thenumber of pins available under the DIMM standard.

In this embodiment, one of the Zynq® computational FPGAs (416 a to 416e) can act as arbiter providing a memory cache, giving an ability tohave peer to peer sharing of data (via memcached or OMQ memoryformalisms) between the other Zynq® computational FPGAs (416 a to 416e). Traffic departing for the computational FPGAs can be controlledthrough memory mapped I/O. The arbiter queues session data for use, andwhen a computational FPGA asks for address outside of the providedsession, the arbiter can be the first level of retrieval, externalprocessing determination, and predictors set.

FIG. 4-3 shows two possible architectures for a module (e.g., XIMM) in asimulation (Xockets MAX and MIN). Xockets MIN (420 a) can be used inlow-end public cloud servers, containing twenty ARM cores (420 b) spreadacross fourteen DIMM slots in a commodity server which has two Opteronx86 processors and two network interface cards (NICs) (420 c). Thisarchitecture can provide a minimal benefit per Watt of power used.Xockets MAX (422 a) contains eighty ARM cores (422 b) across eight DIMMslots, in a server with two Opteron x86 processors and four NICs (422c). This architecture can provide a maximum benefit per Watt of powerused.

FIG. 4-4 shows a representative power budget for an example of a module(e.g., XIMM) according to a particular embodiment. Each component islisted (424 a, 424 b, 424 c, 424 d) along with its power profile.Average total and total wattages are also listed (426 a, 426 b). Intotal, especially for I/O packet processing with packet sizes on theorder 1 KB in size, module can have a low average power budget that iseasily able to be provided by the 22 V_(dd) pins per DIMM. Additionally,the expected thermal output can be handled by inexpensive conductiveheat spreaders, without requiring additional convective, conductive, orthermoelectric cooling. In certain situations, digital thermometers canbe implemented to dynamically reduce performance (and consequent heatgeneration) if needed.

Operation of one embodiment of a module 430 (e.g., XIMM) using an ARM A9architecture is illustrated with respect to FIG. 4-5. Use of ARM A9architecture in conjunction with an FPGA fabric and memory, in this caseshown as reduced latency DRAM (RLDRAM) 438, can simplify or makespossible zero-overhead context switching, memory compression and CPI, inpart by allowing hardware context switching synchronized with networkqueuing. In this way, there can be a one-to-one mapping between threadand queues. As illustrated, the ARM A9 architecture includes a SnoopControl Unit 432 (SCU). This unit allows one to read out and write inmemory coherently. Additionally, the Accelerator Coherency Port 434(ACP) allows for coherent supplementation of the cache throughout theFPGA 436. The RLDRAM 438 provides the auxiliary bandwidth to read andwrite the ping-pong cache supplement (435): Block1$ and Block2$ duringpacket-level meta-data processing.

The following table (Table 1) illustrates potential states that canexist in the scheduling of queues/threads to XIMM processors and memorysuch as illustrated in FIG. 4-5.

TABLE 1 Queue/Thread State HW treatment Waiting for Ingress All ingressdata has been processed and thread Packet awaits further communication.Waiting for MMIO A functional call to MM hardware (such as HW encryptionor transcoding) was made. Waiting for Rate-limit The thread's resourceconsumption exceeds limit, due to other connections idling. Currentlybeing One of the ARM cores is already processing processed this thread,cannot schedule again. Ready for Selection The thread is ready forcontext selection.These states can help coordinate the complex synchronization betweenprocesses, network traffic, and memory-mapped hardware. When a queue isselected by a traffic manager a pipeline coordinates swapping in thedesired L2 cache (440), transferring the reassembled IO data into thememory space of the executing process. In certain cases, no packets arepending in the queue, but computation is still pending to serviceprevious packets. Once this process makes a memory reference outside ofthe data swapped, a scheduler can require queued data from a networkinterface card (NIC) to continue scheduling the thread. To provide fairqueuing to a process not having data, the maximum context size isassumed as data processed. In this way, a queue must be provisioned asthe greater of computational resource and network bandwidth resource,for example, each as a ratio of an 800 MHz A9 and 3 Gbps of bandwidth.Given the lopsidedness of this ratio, the ARM core is generallyindicated to be worthwhile for computation having many parallel sessions(such that the hardware's prefetching of session-specific data andTCP/reassembly offloads a large portion of the CPU load) and thoserequiring minimal general purpose processing of data.

Essentially zero-overhead context switching is also possible usingmodules as disclosed in FIG. 4-5. Because per packet processing hasminimum state associated with it, and represents inherent engineeredparallelism, minimal memory access is needed, aside from packetbuffering. On the other hand, after packet reconstruction, the entirememory state of the session can be accessed, and so can require maximalmemory utility. By using the time of packet-level processing to prefetchthe next hardware scheduled application-level service context in twodifferent processing passes, the memory can always be available forprefetching. Additionally, the FPGA 436 can hold a supplemental“ping-pong” cache (435) that is read and written with every contextswitch, while the other is in use. As previously noted, this is enabledin part by the SCU 432, which allows one to read out and write in memorycoherently, and ACP 434 for coherent supplementation of the cachethroughout the FPGA 436. The RLDRAM 438 provides for read and write tothe ping-pong cache supplement 435 (shown as Block1$ and Block2$) duringpacket-level meta-data processing. In the embodiment shown, only locallyterminating queues can prompt context switching.

In operation, metadata transport code can relieve a main or hostprocessor from tasks including fragmentation and reassembly, andchecksum and other metadata services (e.g., accounting, IPSec, SSL,Overlay, etc.). As IO data streams in and out, L1 cache 437 can befilled during packet processing. During a context switch, the lock-downportion of a translation lookaside buffer (TLB) of an L1 cache can berewritten with the addresses corresponding to the new context. In onevery particular implementation, the following four commands can beexecuted for the current memory space.

MRC p15,0,r0,c10,c0,0; read the lockdown register

BIC r0,r0,#1; clear preserve bit

MCR p15,0,r0,c10,c0,0; write to the lockdown register;

write to the old value to the memory mapped Block RAM

This is a small 32 cycle overhead to bear. Other TLB entries can be usedby the XIMM stochastically.

Bandwidths and capacities of the memories can be precisely allocated tosupport context switching as well as applications such as Openflowprocessing, billing, accounting, and header filtering programs.

For additional performance improvements, the ACP 434 can be used notjust for cache supplementation, but hardware functionalitysupplementation, in part by exploitation of the memory space allocation.An operand can be written to memory and the new function called, throughcustomizing specific Open Source libraries, so putting the thread tosleep and a hardware scheduler can validate it for scheduling again oncethe results are ready. For example, OpenVPN uses the OpenSSL library,where the encrypt/decrypt functions 439 can be memory mapped. Largeblocks are then available to be exported without delay, or consuming theL2 cache 440, using the ACP 434. Hence, a minimum number of calls areneeded within the processing window of a context switch, improvingoverall performance.

FIG. 5-1 is a block diagram of a processing module 500 according toanother embodiment. A processing module 500 can be one implementation ofXIMM as described herein. A processing module 500 can include a physicalin-line module connector 502, a memory interface 504, arbiter logic 506,offload processor(s) 508, local memory 510, and control logic 512. Aconnector 502 can provide a physical connection to system memory bus.This is in contrast to a host processor which can access a system memorybus via a memory controller, or the like. In very particularembodiments, a connector 502 can be compatible with a dual in-linememory module (DIMM) slot of a computing system. Accordingly, a systemincluding multiple DIMM slots can be populated with one or moreprocessing modules 500, or a mix of processing modules and DIMM modules.

A memory interface 504 can detect data transfers on a system memory bus,and in appropriate cases, enable write data to be stored in theprocessing module 500 and/or read data to be read out from theprocessing module 500. In some embodiments, a memory interface 504 canbe a slave interface, thus data transfers are controlled by a masterdevice separate from the processing module. In very particularembodiments, a memory interface 504 can be a direct memory access (DMA)slave, to accommodate DMA transfers over a system memory initiated by aDMA master. Such a DMA master can be a device different from a hostprocessor. In such configurations, processing module 500 can receivedata for processing (e.g., DMA write), and transfer processed data out(e.g., DMA read) without consuming host processor resources.

Arbiter logic 506 can arbitrate between conflicting data accesses withinprocessing module 500. In some embodiments, arbiter logic 506 canarbitrate between accesses by offload processor 508 and accessesexternal to the processor module 500. It is understood that a processingmodule 500 can include multiple locations that are operated on at thesame time. It is also understood that accesses that are arbitrated byarbiter logic 506 can include accesses to physical system memory spaceoccupied by the processor module 500, as well as accesses to resources(e.g., processor resources). Accordingly, arbitration rules for arbiterlogic 506 can vary according to application. In some embodiments, sucharbitration rules are fixed for a given processor module 500. In suchcases, different applications can be accommodated by switching outdifferent processing modules. However, in alternate embodiments, sucharbitration rules can be configurable while the module is connected to adata bus.

Offload processor(s) 508 can include one or more processors that canoperate on data transferred over the system memory bus. In someembodiments, offload processors can run a general operating system,enabling processor contexts to be saved and retrieved. Computing tasksexecuted by offload processor 508 can be controlled by control logic512. Offload processor(s) 508 can operate on data buffered in theprocessing module 500. In addition or alternatively, offloadprocessor(s) 508 can access data stored elsewhere in a system memoryspace. In some embodiment, offload processor(s) 508 can include a cachememory configured to store context information. An offload processor(s)508 can include multiple cores or one core.

A processing module 500 can be included in a system having a hostprocessor (not shown). In some embodiments, offload processors 508 canbe a different type of processor as compared to the host processor. Inparticular embodiments, offload processors 508 can consume less powerand/or have less computing power than a host processor. In veryparticular embodiments, offload processors 508 can be “wimpy” coreprocessors, while a host processor can be a “brawny” core processor. Inalternate embodiments, offload processors 508 can have equivalent orgreater computing power than any host processor.

Local memory 510 can be connected to offload processor(s) 508 to enablethe storing of context information. Accordingly, offload processor(s)508 can store current context information, and then switch to a newcomputing task, then subsequently retrieve the context information toresume the prior task. In very particular embodiments, local memory 510can be a low latency memory with respect to other memories in a system.In some embodiments, storing of context information can include copyinga cache of an offload processor 508 to the local memory 510.

In some embodiments, a same space within local memory 510 is accessibleby multiple offload processors 508 of the same type. In this way, acontext stored by one offload processor can be resumed by a differentoffload processor.

Control logic 512 can control processing tasks executed by offloadprocessor(s) 508. In some embodiments, control logic 512 can beconsidered a hardware scheduler that can be conceptualized as includinga data evaluator 514, scheduler 516 and a switch controller 518. A dataevaluator 514 can extract “metadata” from write data transferred over asystem memory bus. “Metadata”, as used herein, can be any informationembedded at one or more predetermined locations of a block of write datathat indicates processing to be performed on all or a portion of theblock of write data. In some embodiments, metadata can be data thatindicates a higher level organization for the block of write data. Asbut one very particular embodiment, metadata can be header informationof network packet (which may or may not be encapsulated within a higherlayer packet structure).

A scheduler 516 can order computing tasks for offload processor(s) 508.In some embodiments, scheduler 516 can generate a schedule that iscontinually updated as write data for processing is received. In veryparticular embodiments, a scheduler 516 can generate such a schedulebased on the ability to switch contexts of offload processor(s) 508. Inthis way, module computing priorities can be adjusted on the fly. Invery particular embodiments, a scheduler 516 can assign a portion ofphysical address space to an offload processor 508, according tocomputing tasks. The offload processor 508 can then switch between suchdifferent spaces, saving context information prior to each switch, andsubsequently restoring context information when returning to the memoryspace.

Switch controller 518 can control computing operations of offloadprocessor(s) 508. In particular embodiments, according to scheduler 516,switch controller 518 can order offload processor(s) 510 to switchcontexts. It is understood that a context switch operation can be an“atomic” operation, executed in response to a single command from switchcontroller 518. In addition or alternatively, a switch controller 518can issue an instruction set that stores current context information,recalls context information, etc.

In some embodiments, processing module 500 can include a buffer memory(not shown). A buffer memory can store received write data on-board theprocessor module 500. A buffer memory can be implemented on an entirelydifferent set of memory devices, or can be a memory embedded with logicand/or the offload processor. In the latter case, arbiter logic 506 canarbitrate access to the buffer memory. In some embodiments, a buffermemory can correspond to a portion of a system physical memory space.The remaining portion of the system memory space can correspond to otherlike processor modules and/or memory modules connected to the samesystem memory bus. In some embodiments buffer memory can be differentthan local memory 510. For example, buffer memory can have a sloweraccess time than a local memory 510. However, in other embodiments,buffer memory and local memory can be implemented with like memorydevices.

In very particular embodiments, write data for processing can have anexpected maximum flow rate. A processor module 500 can be configured tooperate on such data at, or faster than, such a flow rate. In this way,a master device (not shown) can write data to a processor module withoutdanger of overwriting data “in process”.

The various computing elements of a processor module 500 can beimplemented as one or more integrated circuit devices (ICs). It isunderstood that the various components shown in FIG. 5-1 can be formedin the same or different ICs. For example, control logic 512, memoryinterface 514, and/or arbiter logic 506 can be implemented on one ormore logic ICs, while offload processor(s) 508 and local memory 510 areseparate ICs. Logic ICs can be fixed logic (e.g., application specificICs), programmable logic (e.g., field programmable gate arrays, FPGAs),or combinations thereof.

FIG. 5-2 shows a processor module 500-1 according to one very particularembodiment. A processor module 500-1 can include ICs 520-0/1 mounted toa printed circuit board (PCB) type substrate 522. PCB type substrate 522can include in-line module connection 502, which in one very particularembodiment can be a DIMM compatible connection. IC 520-0 can be asystem-on-chip (SoC) type device, integrating multiple functions. In thevery particular embodiment shown, an IC 520-0 can include embeddedprocessor(s), logic and memory. Such embedded processor(s) can beoffload processor(s) 508 as described herein, or equivalents. Such logiccan be any of controller logic 512, memory interface 504 and/or arbiterlogic 506, as described herein, or equivalents. Such memory can be anyof local memory 510, cache memory for offload processor(s) 508, orbuffer memory, as described herein, or equivalents. Logic IC 520-1 canprovide logic functions not included IC 520-0.

FIG. 5-3 shows a processor module 500-2 according to another veryparticular embodiment. A processor module 500-2 can include ICs 520-2,-3, -4, -5 mounted to a PCB type substrate 522, like that of FIG. 5-2.However, unlike FIG. 5-2, processor module functions are distributedamong single purpose type ICs. IC 520-2 can be a processor IC, which canbe an offload processor 508. IC 520-3 can be a memory IC which caninclude local memory 510, buffer memory, or combinations thereof. IC520-4 can be a logic IC which can include control logic 512, and in onevery particular embodiment, can be an FPGA. IC 520-5 can be anotherlogic IC which can include memory interface 504 and arbiter logic 506,and in one very particular embodiment, can also be an FPGA.

It is understood that FIGS. 5-2 and 5-3 represent but two of variousimplementations. The various functions of a processor module can bedistributed over any suitable number of ICs, including a single SoC typeIC.

FIG. 5-4 shows an opposing side of a processor module 500-3 according toa very particular embodiment. Processor module 500-3 can include anumber of memory ICs, one shown as 520-5, mounted to a PCB typesubstrate 522, like that of FIG. 5-2. It is understood that variousprocessing and logic components can be mounted on an opposing side tothat shown. Memory ICs 520-5 can be configured to represent a portion ofthe physical memory space of a system. Memory ICs 520-5 can perform anyor all of the following functions: operate independently of otherprocessor module components, providing system memory accessed in aconventional fashion; serve as buffer memory, storing write data thatcan be processed with other processor module components; or serve aslocal memory for storing processor context information.

FIG. 5-4 can also represent a conventional DIMM module (i.e., it servesonly a memory function) that can populate a memory bus along withprocessor modules as described herein, or equivalents.

FIG. 5-5 shows a system 530 according to one embodiment. A system 530can include a system memory bus 528 accessible via multiple in-linemodule slots (one shown as 526). According to embodiments, any or all ofthe slots 526 can be occupied by a processor module 500 as describedherein, or an equivalent. In the event all slots 526 are not occupied bya processor module 500, available slots can be occupied by conventionalin-line memory modules 524. In a very particular embodiment, slots 526can be DIMM slots.

In some embodiments, a processor module 500 can occupy one slot.However, in other embodiments, a processor module can occupy multipleslots (i.e., include more than one connection). In some embodiments, asystem memory bus 528 can be further interfaced with one or more hostprocessors and/or input/output devices (not shown).

Having described processor modules according to various embodiments,operations of a processor module according to particular embodimentswill now be described. FIGS. 5-6 to 5-11 show processor moduleoperations according to various embodiments. FIGS. 5-10 to 5-15 show aprocessor module like that of FIG. 5-1, along with a system memory bus528, and a buffer memory 532. It is understood that in some embodiments,a buffer memory 532 can part of processor module 500. In such a case,arbitration between accesses via system memory 528 and offloadprocessors can be controlled by arbiter logic 506.

Referring to FIG. 5-6, write data 534-0 can be received on system memorybus 528 (circle “1”). In some embodiments, such an action can includethe writing of data to a particular physical address space range of asystem memory. In a very particular embodiment, such an action can be aDMA write independent of any host processor. Write data 534-0 caninclude metadata (MD) as well as data to be processed (Data). In theembodiment shown, write data 534-0 can correspond to a particularprocessing operation (Session0).

Control logic 512 can access metadata (MD) of the write data 534-0 todetermine a type of processing to be performed (circle “2”). In someembodiments, such an action can include a direct read from a physicaladdress (i.e., MD location is at a predetermined location). In additionor alternatively, such an action can be an indirect read (i.e., MD isaccessed via pointer, or the like). The action shown by circle “2” canbe performed by any of: a read by control logic 512 or read by anoffload processor 508. From extracted metadata, scheduler 516 can createa processing schedule, or modify an existing schedule to accommodate thenew computing task (circle “3”).

Referring to FIG. 5-7, in response to a scheduler 516, switch controller518 can direct one or more offload processors 508 be begin processingdata according to MD of the write data (circles “4”, “5”). Suchprocessing of data can include any of the following and equivalents:offload processor 508 can process write data stored in a buffer memoryof the processor module 500, with accesses being arbitrated by arbiterlogic 506; offload processor 508 can operate on data previouslyreceived; offload processor 508 can receive and operation on data storedat a location different than the processor module 500.

Referring to FIG. 5-8, additional write data 534-1 can be received onsystem memory bus 528 (circle “6”). Write data 534-1 can include MD thatindicates a different processing operation (Session1) than that forwrite data 534-0. Control logic 512 can access metadata (MD) of the newwrite data 534-1 to determine a type of processing to be performed(circle “7”). From extracted metadata, scheduler 516 can modify thecurrent schedule to accommodate the new computing task (circle “8”). Inthe particular example shown, the modified schedule re-tasks offloadprocessor(s) 508. Thus, switch controller 518 can direct an offloadprocessor 508 to store its current context (ContextA) in local memory510 (circle “9”).

Referring to FIG. 5-9, in response to switch controller 518, offloadprocessor(s) 508 can begin the new processing task (circle “10”).Consequently, offload processor(s) 508 can maintain a new context(ContextB) corresponding to the new processing task.

Referring to FIG. 5-10, a processing task by offload processor 508 canbe completed. In the very particular embodiment shown, such processingcan modify write data (534-1) and such modified data 534-1′ can be readout over system memory bus 528 (circle “11”). In response to thecompletion of processing task, scheduler 516 can update a schedule. Inthe example shown, in response to the updated schedule, switchcontroller 518 can direct offload processor(s) 508 to restore thepreviously saved context (ContextA) from local memory 510 (circle “12”).As understood from above, in some particular embodiments, a restoredcontext (e.g., ContextA) may have been stored by an offload processordifferent from the one that saved the context in the first place.

Referring to FIG. 5-11, with a previous context restored, offloadprocessor(s) 508 can return to processing data according to the previoustask (Session0) (circle “13”).

FIG. 5-12 shows a method 540 according an embodiment. A method 540 caninclude detecting the write of session data to a system memory with anin-line module slave interface 542. Such an action can includedetermining if received write data has metadata (i.e., data identifyinga particular processing). It is understood that “session data” is datacorresponding to a particular processing task. Further, it is understoodthat MD accompanying (or embedded within) session data can identify thepriority of a session with respect to other sessions.

A method 540 can determine if current offload processing is sufficientfor a new session or change of session 544. Such an action take intoaccount a processing time required for any current sessions.

If current processing resources can accommodate new session requirements(Y from 544), a hardware schedule (schedule for controlling offloadprocessor(s)) can be revised and the new session can be assigned to anoffload processor. If current processing resources cannot accommodatenew session requirements (N from 544), one or more offload processorscan be selected for re-tasking (e.g., a context switch) 550 and thehardware schedule can be modified accordingly 552. The selected offloadprocessors can save their current context data 554 and then switch tothe new session 556.

FIG. 5-13 shows a method 560 according another embodiment. A method 560can include determining if a computing session for an offload processoris complete 562 or has been terminated 564. In such cases (Y from562/564), it can be determined if the free in-line module offloadprocessor (i.e., an offload processor whose session iscomplete/terminated) has a stored context 566. That is, it can bedetermined if the free processor was previously operating on a session.

If a free offload processor was operating according to another session(Y from 566), the offload processor can restore the previous context568. If a free offload processor has no stored context, it can beassigned to an existing session (if possible) 570. An existing hardwareschedule can be updated correspondingly 572.

Processor modules according to embodiments herein can be employed toaccomplish various processing tasks. According to some embodiments,processor modules can be attached to a system memory bus to operate onnetwork packet data. Such embodiments will now be described.

FIG. 6-1 shows a system 601 that can transport packet data to one ormore computational units (one shown as 600) located on a module, whichin particular embodiments, can include a connector compatible with anexisting memory module. In some embodiments, a computational unit 600can include a processor module (e.g., XIMM) as described in embodimentsherein, or an equivalent. A computational unit 600 can be capable ofintercepting or otherwise accessing packets sent over a memory bus 616and carrying out processing on such packets, including but not limitedto termination or metadata processing. A system memory bus 616 can be asystem memory bus like those described herein, or equivalents (e.g.,528).

According to some embodiments, packets corresponding to a particularflow can be transported to a storage location accessible by, or includedwithin computational unit 600. Such transportation can occur withoutconsuming resources of a host processor module 606 c connected to memorybus 616. In particular embodiments, such transport can occur withoutinterrupting the host processor module 606 c. In such an arrangement, ahost processor module 606 c does not have to handle incoming flows.Incoming flows can be directed to computational unit 600, which inparticular embodiments can include one or more general purposeprocessors 608 i. Such general purpose processors 608 i can be capableof running code for terminating incoming flows.

In one very particular embodiment, a general purpose processor 608 i canrun code for terminating particular network flow session types, such asApache video sessions, as but one example.

In addition or alternatively, a general purpose processor 608 i canprocess metadata of a packet. In such embodiments, such metadata caninclude one or more fields of a header for the packet, or a headerencapsulated further within the packet.

Referring still to FIG. 6-1, according to embodiments, a system 601 cancarry out any of the following functions: 1) transport packets of a flowto a destination occupied by, or accessible by, a computational unit 600without interrupting a host processor module 606 c; 2) transport packetsto an offload processor 608 i capable of terminating session flows(i.e., the offload processor is responsible for terminating sessionflows); 3) transport packets to a midplane switch that can process themetadata associated with a packet and make a switching decision; or 4)provide a novel high speed packet terminating system.

Conventional packet processing systems can utilize host processors forpacket termination. However, due to the context switching involved inhandling multiple sessions, conventional approaches require significantprocessing overhead for such context switching, and can incur memoryaccess and network stack delay.

In contrast to conventional approaches, embodiments as disclosed hereincan enable high speed packet termination by reducing context switchoverhead of a host processor. Embodiments can provide any of thefollowing functions: 1) offload computation tasks to one or moreprocessors via a system memory bus, without the knowledge of the hostprocessor, or significant host processor involvement; 2) interconnectservers in a rack or amongst racks by employing offload processors asswitches; or 3) use I/O virtualization to redirect incoming packets todifferent offload processors.

Referring still to FIG. 6-1, a system 601 can include an I/O device 602which can receive packet or other I/O data from an external source. Insome embodiments I/O device 602 can include physical or virtualfunctions generated by the physical device to receive a packet or otherI/O data from the network or another computer or virtual machine. In thevery particular embodiment shown, an I/O device 602 can include anetwork interface card (NIC) having input buffer 602 a (e.g., DMA ringbuffer) and an I/O virtualization function 602 b.

According to embodiments, an I/O device 602 can write a descriptorincluding details of the necessary memory operation for the packet (i.e.read/write, source/destination). Such a descriptor can be assigned avirtual memory location (e.g., by an operating system of the system601). I/O device 602 can communicate with an input output memorymanagement unit (IOMMU) 604 which can translate virtual addresses tocorresponding physical addresses. In the particular embodiment shown, atranslation look-aside buffer (TLB) 604 a can be used for suchtranslation. Virtual function reads or writes data between I/O deviceand system memory locations can then be executed with a direct memorytransfer (e.g., DMA) via a memory controller 606 b of the system 601. AnI/O device 602 can be connected to IOMMU 604 b by a host bus 612. In onevery particular embodiment, a host bus 612 can be a peripheralinterconnect (PCI) type bus. IOMMU 604 b can be connected to a hostprocessing section 606 at a central processing unit I/O (CPUIO) 606 a.In the embodiment shown, such a connection 664 can support aHyperTransport (HT) protocol.

In the embodiment shown, a host processing section 606 can include theCPUIO 606 a, memory controller 606 b, host processor module 606 c andcorresponding provisioning agent 606 d.

In particular embodiments, a computational unit 600 can interface withthe system bus 616 via standard in-line module connection, which in veryparticular embodiments can include a DIMM type slot. In the embodimentshown, a memory bus 616 can be a DDR3 type memory bus, however alternateembodiments can include any suitable system memory bus. Packet data canbe sent by memory controller 606 b to via memory bus 616 to a DMA slaveinterface 610 a. DMA slave interface 610 a can be adapted to receiveencapsulated read/write instructions from a DMA write over the memorybus 616.

A hardware scheduler (608 b/c/d/e/h) can perform traffic management onincoming packets by categorizing them according to flow using sessionmetadata. Packets can be queued for output in an onboard memory (610b/608 a/608 m) based on session priority. When the hardware schedulerdetermines that a packet for a particular session is ready to beprocessed by the offload processor 608 i, the onboard memory is signaledfor a context switch to that session. Utilizing this method ofprioritization, context switching overhead can be reduced, as comparedto conventional approaches. That is, a hardware scheduler can handlecontext switching decisions and thus optimizing the performance of thedownstream resource (e.g., offload processor 608 i).

As noted above, in very particular embodiments, an offload processor 608i can be a “wimpy” core type processor. According to some embodiments, ahost processor module 606 c can include a “brawny” core type processor(e.g., an x86 or any other processor capable of handling “heavy touch”computational operations). While an I/O device 602 can be configured totrigger host processor interrupts in response to incoming packets,according to embodiments, such interrupts can be disabled, therebyreducing processing overhead for the host processor module 606 c. Insome very particular embodiments, an offload processor 608 i can includean ARM, ARC, Tensilica, MIPS, Strong/ARM or any other processor capableof handling “light touch” operations. Preferably, an offload processorcan run a general purpose operating system for executing a plurality ofsessions, which can be optimized to work in conjunction with thehardware scheduler in order to reduce context switching overhead.

Referring still to FIG. 6-1, in operation, a system 601 can receivepackets from an external network over a network interface. The packetscan be directed for processing by either a host processor module 606 cor an offload processor 608 i based on the classification logic andschematics employed by I/O device 602. In particular embodiments, I/Odevice 602 can operate as a virtualized NIC, with packets for aparticular logical network or to a certain virtual MAC (VMAC) addressbeing directed into separate queues and sent over to the destinationlogical entity. Such an arrangement can transfer packets to differententities. In some embodiments, each such entity can have a virtualdriver, a virtual device model that it uses to communicate with virtualnetwork interfaces it is connected to.

According to embodiments, multiple devices can be used to redirecttraffic to specific memory addresses. So, each of the network devicesoperates as if it is transferring the packets to the memory location ofa logical entity. However, in reality, such packets can be transferredto memory addresses where they can be handled by one or more offloadprocessors. In particular embodiments such transfers are to physicalmemory addresses, thus logical entities can be removed from theprocessing, and a host processor can be free from such packet handling.

Accordingly, embodiments can be conceptualized as providing a memory“black box” to which specific network data can be fed. Such a memoryblack box can handle the data (e.g., process it) and respond back whensuch data is requested.

Referring still to FIG. 6-1, according to some embodiments, I/O device602 can receive data packets from a network or from a computing device.The data packets can have certain characteristics, including transportprotocol number, source and destination port numbers, source anddestination IP addresses, for example. The data packets can further havemetadata that is processed (608 d) that helps in their classificationand management.

I/O device 602 can include, but is not limited to, peripheral componentinterconnect (PCI) and/or PCI express (PCIe) devices connecting withhost motherboard via PCI or PCIe bus (e.g., 612). Examples of I/Odevices include a network interface controller (NIC), a host busadapter, a converged network adapter, an ATM network interface etc.

In order to provide for an abstraction scheme that allows multiplelogical entities to access the same I/O device 602, the I/O device maybe virtualized to provide for multiple virtual devices each of which canperform some of the functions of the physical I/O device. The IOvirtualization program, according to an embodiment, can redirect trafficto different memory locations (and thus to different offload processorsattached to modules on a memory bus). To achieve this an I/O device 602(e.g., a network card) may be partitioned into several function parts;including controlling function (CF) supporting input/outputvirtualization (IOV) architecture (e.g., single-root IOV) and multiplevirtual function (VF) interfaces. Each virtual function interface may beprovided with resources during runtime for dedicated usage. Examples ofthe CF and VF may include the physical function and virtual functionsunder schemes such as Single Root I/O Virtualization or Multi-Root I/OVirtualization architecture. The CF acts as the physical resources thatsets up and manages virtual resources. The CF is also capable of actingas a full-fledged IO device. The VF is responsible for providing anabstraction of a virtual device for communication with multiple logicalentities/multiple memory regions.

The operating system/the hypervisor/any of the virtual machines/usercode running on a host processor module 606 c may be loaded with adevice model, a VF driver and a driver for a CF. The device model may beused to create an emulation of a physical device for the host processor606 c to recognize each of the multiple VFs that are created. The devicemodel may be replicated multiple times to give the impression to a VFdriver (a driver that interacts with a virtual IO device) that it isinteracting with a physical device of a particular type.

For example, a certain device module may be used to emulate a networkadapter such as the Intel® Ethernet Converged Network Adapter (CNA)X540-T2, so that the I/O device 602 believes it is interacting with suchan adapter. In such a case, each of the virtual functions may have thecapability to support the functions of the above said CNA, i.e., each ofthe Physical Functions should be able to support such functionality. Thedevice model and the VF driver can be run in either privileged ornon-privileged modes. In some embodiments, there is no restriction withregard to who hosts/runs the code corresponding to the device model andthe VF driver. The code, however, has the capability to create multiplecopies of device model and VF driver so as to enable multiple copies ofsaid I/O interface to be created.

An application or provisioning agent 606 d, as part of anapplication/user level code running in a kernel, may create a virtualI/O address space for each VF during runtime and allocate part of thephysical address space to it. For example, if an application handlingthe VF driver instructs it to read or write packets from or to memoryaddresses 0xaaaa to 0xffff, the device driver may write I/O descriptorsinto a descriptor queue with a head and tail pointer that are changeddynamically as queue entries are filled. The data structure may be ofanother type as well, including but not limited to a ring structure 602a or hash table.

The VF can read from or write data to the address location pointed to bythe driver (and hence to a computational unit 600). Further, oncompleting the transfer of data to the address space allocated to thedriver, interrupts, which are usually triggered to the host processor tohandle said network packets, can be disabled. Allocating a specific I/Ospace to a device can include allocating said IO space a specificphysical memory space occupied.

In another embodiment, the descriptor may comprise only a writeoperation, if the descriptor is associated with a specific datastructure for handling incoming packets. Further, the descriptor foreach of the entries in the incoming data structure may be constant so asto redirect all data write to a specific memory location. In analternate embodiment, the descriptor for consecutive entries may pointto consecutive entries in memory so as to direct incoming packets toconsecutive memory locations.

Alternatively, said operating system may create a defined physicaladdress space for an application supporting the VF drivers and allocatea virtual memory address space to the application or provisioning agent606 d, thereby creating a mapping for each virtual function between saidvirtual address and a physical address space. Said mapping betweenvirtual memory address space and physical memory space may be stored inIOMMU tables 604 a. The application performing memory reads or writesmay supply virtual addresses to say virtual function, and the hostprocessor OS may allocate a specific part of the physical memorylocation to such an application.

Alternatively, VF may be configured to generate requests such as readand write which may be part of a direct memory access (DMA) read orwrite operation, for example. The virtual addresses is be translated bythe IOMMU 604 b to their corresponding physical addresses and thephysical addresses may be provided to the memory controller for access.That is, the IOMMU 604 b may modify the memory requests sourced by theI/O devices to change the virtual address in the request to a physicaladdress, and the memory request may be forwarded to the memorycontroller for memory access. The memory request may be forwarded over abus 614. The VF may in such cases carry out a direct memory access bysupplying the virtual memory address to the IOMMU 604 b.

Alternatively, said application may directly code the physical addressinto the VF descriptors if the VF allows for it. If the VF cannotsupport physical addresses of the form used by the host processor 606 c,an aperture with a hardware size supported by the VF device may be codedinto the descriptor so that the VF is informed of the target hardwareaddress of the device. Data that is transferred to an aperture may bemapped by a translation table to a defined physical address space in thesystem memory. The DMA operations may be initiated by software executedby the processors, programming the I/O devices directly or indirectly toperform the DMA operations.

Referring still to FIG. 6-1, in particular embodiments, parts ofcomputational unit 600 can be implemented with one or more FPGAs. In thesystem of FIG. 6-1, computational unit 600 can include FPGA 610 in whichcan be formed a DMA slave device module 610 a and arbiter 610 f. A DMAslave module 610 a can be any device suitable for attachment to a memorybus 616 that can respond to DMA read/write requests. In alternateembodiments, a DMA slave module 610 a can be another interface capableof block data transfers over memory bus 616. The DMA slave module 610 acan be capable of receiving data from a DMA controller (when it performsa read from a ‘memory’ or from a peripheral) or transferring data to aDMA controller (when it performs a write instruction on the DMA slavemodule 610 a). The DMA slave module 610 a may be adapted to receive DMAread and write instructions encapsulated over a memory bus, (e.g., inthe form of a DDR data transmission, such as a packet or data burst), orany other format that can be sent over the corresponding memory bus.

A DMA slave module 610 a can reconstruct the DMA read/write instructionfrom the memory R/W packet. The DMA slave module 610 a may be adapted torespond to these instructions in the form of data reads/data writes to aDMA master, which could either be housed in a peripheral device, in thecase of a PCIe bus, or a system DMA controller in the case of an ISAbus.

I/O data that is received by the DMA device 610 a can then be queued forarbitration. Arbitration is the process of scheduling packets ofdifferent flows, such that they are provided access to availablebandwidth based on a number of parameters. In general, an arbiterprovides resource access to one or more requestors. If multiplerequestors request access, an arbiter 610 f can determine whichrequestor becomes the accessor and then passes data from the accessor tothe resource interface, and the downstream resource can begin executionon the data. After the data has been completely transferred to aresource, and the resource has competed execution, the arbiter 610 f cantransfer control to a different requestor and this cycle repeats for allavailable requestors. In the embodiment of FIG. 6-1, arbiter 610 f cannotify other portions of computational unit 600 (e.g., 608) of incomingdata.

Alternatively, a computation unit 600 can utilize an arbitration schemeshown in U.S. Pat. No. 7,863,283, issued to Dalal on Oct. 62, 2010, thecontent of which are incorporated herein by reference. Other suitablearbitration schemes known in art could be implemented in embodimentsherein. Alternatively, the arbitration scheme for an embodiment can bean OpenFlow switch and an OpenFlow controller.

In the very particular embodiment of FIG. 6-1, computational unit 600can further include notify/prefetch circuits 610 c which can prefetchdata stored in a buffer memory 610 b in response to DMA slave module 610a, and as arbitrated by arbiter 610 f. Further, arbiter 610 f can accessother portions of the computational unit 600 via a memory mapped I/Oingress path 610 e and egress path 610 g.

Referring to FIG. 6-1, a hardware scheduler can include a schedulingcircuit 608 b/n to implement traffic management of incoming packets.Packets from a certain source, relating to a certain traffic class,pertaining to a specific application or flowing to a certain socket arereferred to as part of a session flow and are classified using sessionmetadata. Such classification can be performed by classifier 608 e.

In some embodiments, session metadata 608 d can serve as the criterionby which packets are prioritized and scheduled and as such, incomingpackets can be reordered based on their session metadata. Thisreordering of packets can occur in one or more buffers and can modifythe traffic shape of these flows. The scheduling discipline chosen forthis prioritization, or traffic management (TM), can affect the trafficshape of flows and micro-flows through delay (buffering), bursting oftraffic (buffering and bursting), smoothing of traffic (buffering andrate-limiting flows), dropping traffic (choosing data to discard so asto avoid exhausting the buffer), delay jitter (temporally shifting cellsof a flow by different amounts) and by not admitting a connection (e.g.,cannot simultaneously guarantee existing service (SLAB) with anadditional flow's SLA).

According to embodiments, computational unit 600 can serve as part of aswitch fabric, and provide traffic management with depth-limited outputqueues, the access to which is arbitrated by a scheduling circuit 608b/n. Such output queues are managed using a scheduling discipline toprovide traffic management for incoming flows. The session flows queuedin each of these queues can be sent out through an output port to adownstream network element.

It is noted that some conventional traffic management circuits do nottake into the account the handling and management of data by downstreamelements except for meeting the SLA agreements it already has with saiddownstream elements. In contrast, according to embodiments, a schedulercircuit 608 b/n can allocate a priority to each of the output queues andcarry out reordering of incoming packets to maintain persistence ofsession flows in these queues. A scheduler circuit 608 b/n can be usedto control the scheduling of each of these persistent sessions into ageneral purpose operating system (OS) 608 j, executed on an offloadprocessor 608 i. Packets of a particular session flow, as defined above,can belong to a particular queue. The scheduler circuit 608 b/n maycontrol the prioritization of these queues such that they are arbitratedfor handling by a general purpose (GP) processing resource (e.g.,offload processor 608 i) located downstream. An OS 608 j running on adownstream processor 608 i can allocate execution resources such asprocessor cycles and memory to a particular queue it is currentlyhandling. The OS 608 j may further allocate a thread or a group ofthreads for that particular queue, so that it is handled distinctly bythe general purpose processing element 608 i as a separate entity. Thus,in some embodiments there can be multiple sessions running on a GPprocessing resource, each handling data from a particular session flowresident in a queue established by the scheduler circuit, to tightlyintegrate the scheduler and the downstream resource (e.g., 608 i). Thiscan bring about persistence of session information across the trafficmanagement and scheduling circuit and the general purpose processingresource 608 j.

Dedicated computing resources (e.g., 608 i), memory space and sessioncontext information for each of the sessions can provide a way ofhandling, processing and/or terminating each of the session flows at thegeneral purpose processor 608 i. The scheduler circuit 608 b/n canexploit this functionality of the execution resource to queue sessionflows for scheduling downstream. For example, the scheduler circuit 608b/n can be informed of the state of the execution resource(s) (e.g., 608i), the current session that is run on the execution resource; thememory space allocated to it, the location of the session context in theprocessor cache.

According to embodiments, a scheduler circuit 608 b/n can furtherinclude switching circuits to change execution resources from one stateto another. The scheduler circuit 608 b/n can use such a capability toarbitrate between the queues that are ready to be switched into thedownstream execution resource. Further, the downstream executionresource can be optimized to reduce the penalty and overhead associatedwith context switch between resources. This is further exploited by thescheduler circuit 608 b/n to carry out seamless switching betweenqueues, and consequently their execution as different sessions by theexecution resource.

A scheduler circuit 608 b/n according to embodiments can scheduledifferent sessions on a downstream processing resource, wherein the twoare operated in coordination to reduce the overhead during contextswitches. An important factor to decreasing the latency of services andengineering computational availability can be hardware context switchingsynchronized with network queuing. In embodiments, when a queue isselected by a traffic manager, a pipeline coordinates swapping in of thecache (e.g., L2 cache) of the corresponding resource and transfers thereassembled I/O data into the memory space of the executing process. Incertain cases, no packets are pending in the queue, but computation isstill pending to service previous packets. Once this process makes amemory reference outside of the data swapped, the scheduler circuit canenable queued data from an I/O device 602 to continue scheduling thethread.

In some embodiments, to provide fair queuing to a process not havingdata, a maximum context size can be assumed as data processed. In thisway, a queue can be provisioned as the greater of computational resourceand network bandwidth resource.

As but one very particular example, a computation resource can be an ARMA9 processor running at 800 MHz, while a network bandwidth can be 3 Gbpsof bandwidth. Given the lopsided nature of this ratio, embodiments canutilize computation having many parallel sessions (such that thehardware's prefetching of session-specific data offloads a large portionof the host processor load) and having minimal general purposeprocessing of data.

Accordingly, in some embodiments, a scheduler circuit 608 b/n can beconceptualized as arbitrating, not between outgoing queues at line ratespeeds, but arbitrating between terminated sessions at very high speeds.The stickiness of sessions across a pipeline of stages, including ageneral purpose OS, can be a scheduler circuit optimizing any or allsuch stages of such a pipeline.

Alternatively, a scheduling scheme can be used as shown in U.S. Pat. No.7,760,765 issued to Dalal on Jul. 20, 2010, incorporated herein byreference. This scheme can be useful when it is desirable to rate limitthe flows for preventing the downstream congestion of another resourcespecific to the over-selected flow, or for enforcing service contractsfor particular flows. Embodiments can include arbitration scheme thatallows for service contracts of downstream resources, such as generalpurpose OS that can be enforced seamlessly.

Referring still to FIG. 6-1, a hardware scheduler according toembodiments herein, or equivalents, can provide for the classificationof incoming packet data into session flows based on session metadata. Itcan further provide for traffic management of these flows before theyare arbitrated and queued as distinct processing entities on the offloadprocessors.

In some embodiments, offload processors (e.g., 608 i) can be generalpurpose processing units capable of handling packets of differentapplication or transport sessions. Such offload processors can be lowpower processors capable of executing general purpose instructions. Theoffload processors could be any suitable processor, including but notlimited to: ARM, ARC, Tensilica, MIPS, StrongARM or any other processorthat serves the functions described herein. The offload processors havegeneral purpose OS running on them, wherein the general purpose OS isoptimized to reduce the penalty associated with context switchingbetween different threads or group of threads.

In contrast, context switches on host processors can be computationallyintensive processes that require the register save area, process contextin the cache and TLB entries to be restored if they are invalidated oroverwritten. Instruction Cache misses in host processing systems canlead to pipeline stalls and data cache misses lead to operation stalland such cache misses reduce processor efficiency and increase processoroverhead.

According to embodiments, an OS 608 j running on the offload processors608 i in association with a scheduler circuit, can operate together toreduce the context switch overhead incurred between different processingentities running on it. Embodiments can include a cooperative mechanismbetween a scheduler circuit and the OS on the offload processor 608 i,wherein the OS sets up session context to be physically contiguous(physically colored allocator for session heap and stack) in the cache;then communicates the session color, size, and starting physical addressto the scheduler circuit upon session initialization. During an actualcontext switch, a scheduler circuit can identify the session context inthe cache by using these parameters and initiate a bulk transfer ofthese contents to an external low latency memory. In addition, thescheduler circuit can manage the prefetch of the old session if itscontext was saved to a local memory 608 g. In particular embodiments, alocal memory 608 g can be low latency memory, such as a reduced latencydynamic random access memory (RLDRAM), as but one very particularembodiment. Thus, in embodiments, session context can be identifieddistinctly in the cache.

In some embodiments, context size can be limited to ensure fastswitching speeds. In addition or alternatively, embodiments can includea bulk transfer mechanism to transfer out session context to a localmemory 608 g. The cache contents stored therein can then be retrievedand prefetched during context switch back to a previous session.Different context session data can be tagged and/or identified withinthe local memory 608 m for fast retrieval. As noted above, contextstored by one offload processor may be recalled by a different offloadprocessor.

In the very particular embodiment of FIG. 6-1 multiple offloadprocessing cores can be integrated into a computation FPGA 608. Multiplecomputational FPGAs can be arbitrated by arbitrator circuits in anotherFPGA 610. The combination of computational FPGAs (e.g., 608) and arbiterFPGAs (e.g., 610) can be one implementation of a XIMM module. Inparticular applications, these XIMM modules can provide integratedtraffic and thread management circuits that broker execution of multiplesessions on the offload processors.

FIG. 6-2 shows a system flow according to an embodiment. Packet or otherI/O data can be received at an I/O device 620. An I/O device 620 can bephysical device, virtual device or combination thereof. Interruptsgenerated from the I/O data, that would conventionally be intended for ahost processor 624, can be disabled, allowing such I/O data to beprocessed without resources of the host processor 624.

An IOMMU 621 can map received data to physical addresses of a systemaddress space. DMA master 625 can transmit such data to such memoryaddresses by operation of a memory controller 622. Memory controller 622can execute DRAM transfers over a memory bus with a DMA Slave 627. Uponreceiving transferred I/O data, a hardware scheduler 623 can scheduleprocessing of such data with an offload processor 624. In someembodiments, a type of processing can be indicated by metadata withinthe I/O data. Further, in some embodiments such data can be stored in anOnboard Memory 629. According to instructions from hardware scheduler623, one or more offload processors 624 can execute computing functionsin response to the I/O data. In some embodiments, such computingfunctions can operate on the I/O data, and such data can be subsequentlyread out on memory bus via a read request processed by DMA Slave 627.

It should be appreciated that in the foregoing description of exemplaryembodiments of the invention, various features of the invention aresometimes grouped together in a single embodiment, figure, ordescription thereof for the purpose of streamlining the disclosureaiding in the understanding of one or more of the various inventiveaspects. This method of disclosure, however, is not to be interpreted asreflecting an intention that the claimed invention requires morefeatures than are expressly recited in each claim. Rather, as thefollowing claims reflect, inventive aspects lie in less than allfeatures of a single foregoing disclosed embodiment. Thus, the claimsfollowing the detailed description are hereby expressly incorporatedinto this detailed description, with each claim standing on its own as aseparate embodiment of this invention.

It is also understood that the embodiments of the invention may bepracticed in the absence of an element and/or step not specificallydisclosed. That is, an inventive feature of the invention may beelimination of an element.

Accordingly, while the various aspects of the particular embodiments setforth herein have been described in detail, the present invention couldbe subject to various changes, substitutions, and alterations withoutdeparting from the spirit and scope of the invention.

What is claimed is:
 1. A distributed server system for handling multiple networked applications, comprising: at least one main processor; a plurality of offload processors connected to a memory bus; an arbiter connected to each of the plurality of offload processors, the arbiter configured to schedule resource priority for instructions or data received from the memory bus; and a virtual switch respectively connected to the main processor and the plurality of offload processors using the memory bus, with the virtual switch capable of receiving memory read/write data over the memory bus, and further directing at least some memory read/write data to the arbiter.
 2. The distributed server system of claim 1, wherein the offload processors provide support for a web server and the at least one main processor provides support for at least one of server side script engine, a web page rendering engine, or a database engine.
 3. The distributed server system of claim 1, wherein the offload processors provide support for multimedia streaming data and the at least one main processor provides support for an overlay control.
 4. The distributed server system of claim 1, wherein the offload processors provide support for a proxy server.
 5. The distributed server system of claim 1, wherein the offload processors are connected to memory, and further include a snoop control unit for coherent read out and write in to memory.
 6. The distributed server system of claim 1, wherein the offload processors are connected to memory to permit zero-overhead context switching between threads of a networked application.
 7. The distributed server system of claim 1, wherein the offload processors are connected to memory and a computational FPGA, all being mounted together on XIMM module configured for insertion into a DIMM socket. 